The invention concerns a joint for sealing a pipeline against external fluids, particularly for joining two iron pipes having spigot and socket ends. The invention is applied to hot water pipes covered over most of their length by a layer of foam insulation contained within a protective outer jacket that is impermeable to fluids. The socket and spigot ends of each pipe do not have this outer covering.
French Pat. No. 2,445,925 describes a sealed joint for insulated pipes of this type, using only currently available parts and allowing for a slight angular deviation. This joint includes a rigid outer sleeve made of asbestos cement. The relatively long protrusion of this sleeve with respect to the outer protective covering of the insulating material can be disadvantageous if there is friction in the joint or if the pipes are assembled on the ground. In addition, the rigid outer sleeve that covers the two ends of the exterior casings of the assembled composite pipes requires the installation of washers between the sleeves and the outer casings to protect the insulating layer from external humidity.
U.S. Pat. No. 3,563,572 describes a leaktight and composite assembly of insulated telescoping pipes made of metal and encased in a rigid outer tubing surrounding a layer of insulation. In this assembly a rigid inner locking sleeve, made of insulating material covered with an elastic sealer, joins the two composite pipes without any protrusion over the outer jacket. However, in addition to the fact that such a solution is not applicable to interlocking iron pipes, it does not allow for any angular deviation between the composite pipes because of the presence of the rigid locking sleeve, which must rest on the transverse annular surfaces of the insulating layer. Any angular deviation of the rigid locking sleeve with respect to the insulation would interfere with this transverse support, thereby risking a loss of the seal that protects the layer of insulation from outside moisture. With a small angular deviation, this risk is all the greater because no radial clamping or banding can be used to hold the rigid inner locking sleeve against the rigid outer tubing covering the layer of insulation.